1. Technical Field
The present invention relates to a face collation apparatus that collates a face image.
2. Related Art
Collation accuracy of a face collation apparatus largely depends on a registration condition of a registrant and a collation condition with respect to a collation object person, and the like.
As the registration condition, there are cited, for example, a number of registrants, a number of registration images of the relevant registrant, properties of an imaging device that photographs the registration images (an S/N ratio, shutter speed, exposure, focal distance, photographing number, etc.), and a face size, a lighting environment, invisibility of a face organ, a face direction in the registration image, and so on.
As the collation condition, there are cited, for example, an elapsed time since the registration image is photographed, properties of an imaging device that photographs a collation image, a photographing number of collation images, and a face size, a lighting environment, invisibility of a face organ, a face direction, reliability of face detection, reliability of a feature quantity in the collation image, and so on.
Specifically, when a person other than registrants is collated, as a number of registrants increases, probability that a person resembling the relevant stranger appears among the plurality of registrants becomes higher. Therefore, as the number of registrants increases, a higher score is calculated as an average. In a situation where only one threshold is set for determining whether or not the collation object person is the registrant, the above-described fluctuations in score result in fluctuations in likelihood of acceptance of the stranger (stranger acceptance rate).
These fluctuations in stranger acceptance rate due to the condition means that authentication accuracy of the apparatus fluctuates depending on the condition. In order to perform the face collation at stable authentication accuracy, a face collation apparatus capable of face collation in which the stranger acceptance rate does not depend on the registration condition and the collation condition has been desired.
Conventionally, in order to deal with this problem, an ex-ante adjustment such as finding a correction value of a score matching the condition of the apparatus, finding an appropriate threshold and the like has been performed every time the apparatus is installed.
However, adjustment every time the apparatus is installed is largely burdensome for a user, and inefficient.
As examples of the above-described collation apparatus, there are inventions described in Japanese Patent Application Laid-Open No. 2000-163092, and Japanese Patent Application Laid-Open No. 2001-101406.